JP2935466B2 - Light emission control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emission control device, and more particularly, to a light emission control device that controls strobe light emission in a camera having a low-luminance automatic light emission strobe.

[Prior Art] In a strobe device, in addition to the conventional automatic low-brightness light emission, the camera automatically detects a backlight state and emits a strobe light by obtaining an average brightness and a partial brightness of a subject, respectively. Such is disclosed, for example, in Japanese Patent Publication No. 55-29408. The light emission determination in this case is as shown in Table 3 below, where permission is indicated by a circle and inhibition is indicated by a cross.

[Problems to be Solved by the Invention] However, by obtaining the average luminance and the partial luminance respectively, the camera automatically detects the backlighting state and emits a strobe light, so that the flashlight is emitted.
According to the technical means disclosed in No. 8, for example, when a portrait photograph of a person in a front light state is photographed in a top light state, if the light from above is strong, the shadow of the face part becomes strong, resulting in a poor expression of the photograph. Would. Therefore, in the case of a user who is skilled in correcting this, strobe irradiation is used in combination, but this is a considerably difficult shooting technique for a novice user.

Therefore, an object of the present invention is to provide a light emission control device that solves the above-described problems and controls strobe light emission so that the person has proper exposure when photographing a person with a camera having a low-luminance automatic light emission strobe. To be.

[Means for Solving the Problems] A light emission control device according to the present invention includes: a light meter for measuring the brightness of a subject; a distance detector for detecting a distance to the subject;
Focal length detecting means for detecting the focal length of the taking lens,
A photographing magnification calculating means for calculating a photographing magnification of the subject by using outputs of the distance detecting means and the focal length detecting means; and a control means for controlling strobe light emission. When the photographing magnification is higher than a predetermined value and the photographing magnification by the photographing magnification calculating means is within a predetermined range, the strobe light amount value is lower than the strobe light amount value when the subject luminance by the photometric means is lower than the predetermined value. Wherein the control means inhibits strobe light emission if the subject distance by the distance detection means is longer than a predetermined value,
If the subject distance is shorter than the predetermined value, the strobe light emission is prohibited only when the subject brightness by the photometric means is higher than a predetermined value and the shooting magnification by the shooting magnification calculation means is not within a predetermined range. The above-mentioned predetermined range is characterized in that the photographing magnification is in a range of 1/20 to 1/80.

[Operation] In this light emission control device, when the subject brightness by the photometric unit is higher than a predetermined value and the shooting magnification by the shooting magnification calculation unit is within a predetermined range, the subject brightness by the photometric unit is lower than the predetermined value. Lower than the strobe light value at low
Since the strobe light value is set low, it is possible to prevent the subject from floating white and becoming unnatural, for example, when the subject is a person.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit configuration diagram of an electric circuit of a light emission control device according to an embodiment of the present invention, and an example applied to a camera with a zoom function will be described below. In the figure, the light emission control device controls a distance detection means 10 for detecting a subject distance, a focal length detection means 20 for detecting focal length information of a photographing lens, a photometry means 30 for photometry of subject brightness, and a strobe light emission. A flash light emission control means 40 for controlling the operation of each of the above means and a CPU 1 having a photographing magnification calculation means, a light emission inhibition release means and the like formed on a control program.

The distance detecting means 10 will be described.
The infrared light emitted from the infrared LED 14 whose light emission is controlled by
The light is condensed by the light projecting lens 13 and emitted toward a subject (not shown). The light reflected by the subject is received by the light receiving lens 11
Thereby, an image is formed on the light receiving surface of the PSD (semiconductor position detector) 12. The distance measuring circuit 15 calculates the distance to the subject from the photocurrent of the PSD 12 by a known means.

The focal length detecting means 20 includes a focal length detecting circuit 21 and a potentiometer 22, and calculates a focal length f of the photographing lens from a resistance value of the potentiometer 22 in conjunction with a zoom operation by a zoom mechanism (not shown).

The distance to the subject and the focal length f of the photographing lens are transmitted to the CPU 1. Then, the CPU 1 calculates the photographing magnification β from these two values, f, Find more. In this case, for simplicity It does not matter.

An average photometric light receiving element 32 is connected to a photometric circuit 31 of the photometric means 30. The light receiving element for average photometry 32 measures the subject light through the average photometric lens 33, and the obtained photometric result is transmitted to the CPU 1.

Next, the flash light emission control means 40 for controlling strobe light emission will be described. When a signal is output to the output port O ₁ of CPU1 is H → L, turned on transistor Q103 of the strobe circuit via the resistor R103, thereby the transistor Q101, Q102, resistors R101, R102, step-up transformer T101 is shown The known DC / DC converter circuit connected and configured as described above performs an oscillating operation, and charges the main capacitor C101 via the diodes D101 and D102.

Resistors R1, R2, capacitor C1, pressure substantially the same voltage as the main capacitor C101 min, input to the A / D input port I ₁ of the CPU 1. Thereby, the CPU 1 can monitor the charging voltage of the main capacitor C101 at that time at any time.
Here, main capacitor C101, trigger transformer T102,
Capacitor C103, resistor R109, IGBT (Insulated Gate Bipol
The ar transistor Q104 forms a trigger circuit for the Xe tube 22. The IGBT Q104 is an element that can instantaneously control a large current depending on whether the gate voltage is H or L.

Next, a light emission control circuit of the Xe tube 22 will be described. resistance
R104, R105, R109, IGBTQ104, capacitor C102, diode D
Numeral 104 denotes a voltage doubler circuit, that is, a voltage which is twice the voltage between both ends of the main capacitor C101 between A and K of the Xe tube 22 at the time of light emission, thereby lowering the light emission start voltage of the Xe tube 22. . Transistors Q105, Q106, Q107, Q108 are connected to CPU1
Receiving a light emission signal from the output port O ₂ of which performs a control of the gate of IGBTQ104. Diode D103, resistor R110,
The constant voltage diode Z _D and the capacitor C104 are a power supply circuit for generating a gate voltage of the IGBT Q104.

When light emission signal from the output port O ₂ of the resistor R108 CPU 1 is not applied, the transistors Q108, Q107, Q106 are not turned off, the gate of IGBTG104 are not biased. On the other hand, when the emission signal from the output port O ₂ of CPU1 is applied,
The transistors Q108, Q107, Q106 turn on, and the transistor Q1
Since 05 is turned off, the gate of the IGBT Q104 is biased to H through the resistor R106. Capacitor C103 is connected to resistor R104
The capacitor C102 is charged to the voltage across the main capacitor C101 in advance, and the capacitor C102 is similarly connected to the resistor R1
04, R105, and R109 are charged in advance to the voltage across the main capacitor C101.

When IGBTQ104 turns on, the charge of capacitor C103 is
The primary side of the triggering transformer T102 is discharged through Q104, thereby generating a high voltage on the secondary side of the transformer T102 and ionizing the Xe tube 22. At the same time, the capacitor C1
The cathode of the Xe tube 22 is pulled down to −V _C101 through 02, and as a result, a voltage of 2 × VC 101 is applied between A and K of the Xe tube 22, and light emission of the Xe tube 22 becomes easy. Then, when the Xe tube 22 starts emitting light, the emission current is C101 →
The Xe tube 22 → D104 → C101 discharges, and the Xe tube 22 emits light. Thereafter, the light emission signal output from the output port O ₂ of CPU1 is in the L level, the transistor Q108, Q107, Q106
Is turned off, and the transistor Q105 is turned on at the same time. Therefore, the gate of IGBTQ104 is short-circuited by transistor Q105, and IGBTQ104 is turned off. Accordingly, the capacitor C103 is instantaneously charged with electric charge through the Xe tube 22,
At the same time, the Xe tube 22 stops emitting light. The preparation for the next light emission ends at the same time as this light emission. That is, this circuit
The IGBTQ104 is a circuit having three functions of a trigger circuit for light emission, a voltage doubler circuit, and a main switch element for light emission. The above is the description of the flash light emission control means 40 used in the present embodiment. Thus, the guide number of the strobe can be freely controlled.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. In FIG. 2, first, the distance to the subject measured by the distance detecting means 10 shown in FIG. 1 is compared with the strobe light reaching limit distance ₀ (step S1).
If> _{0 in} step S1, it means that the subject exists outside the reach of the strobe light. Therefore, in order to prevent waste by emitting the strobe light, jump to step S8 to turn off the strobe light emission plug and return. The maximum strobe light reaching distance ₀ is set to the maximum strobe number Gma.
x, where F is the F number determined by external light, Required from. Here, if α is 2, the strobe light is permitted to emit a strobe light up to 4Ev under the main subject, and the strobe light is prohibited after that.

Next, it is checked whether or not the light metering level Ev received by the light receiving element 32 is lower than a predetermined light metering level A, that is, low luminance (step S2). The predetermined photometric level A corresponds to a judgment value in the conventional low-luminance automatic light emission. If it is determined in step S2 that the subject has low brightness, the strobe light emission flag is turned on (step S3), and the guide number GNo
Is calculated by the general guide number calculation formula GNo = FNo × l (step S4).

Returning to step S2, if it is determined that the subject is not low-luminance, it is next determined whether or not the photographing magnification β is between photographing magnifications β ₁ and β ₂ that are often used for photographing a person ( Step S7). In this case, it is sufficient to set β ₁ = 1/20 β ₂ = 1/80. In most cases, daylight synchro photography is a photography technique used when photographing a person in backlight, so On / off of the strobe can be determined based on the criterion in step S7.

When the photographing magnification β corresponds to the magnification normally used when a person is affected, the strobe light emission flag is turned on (step S5), and the guide number calculation is shifted to the 1Ev under side, that is, Double (step S6). The reason for this is that if the guide number calculation is performed normally as in step S4 when there is steady light, the subject person often rises white and becomes unnatural. On the other hand, returning to step S7, if the photographing magnification does not correspond to the magnification normally used when photographing a person, the strobe light emission flag is turned off (step S8) and the routine returns.

Since the availability and guide number GNo of flash emission is determined by the above flow may be controlled the output port O ₂ of CPU1 shown in the first diagram in the imaging sequence. The on / off of the strobe light emission described above is shown in a table. If the photographing magnification β is within the range of a magnification normally used when photographing a person, that is, if β ₁ >β> β ₂ , as shown in Table 1, Also, if the magnification is outside the range of the magnification normally used when photographing a person, that is, β> β ₁ , β ₂ > β, they are as shown in Table 2 below. However, the strobe light emission is indicated by a circle and the non-emission light is indicated by a cross.

In the above embodiments, the description has been made on the assumption that the camera has a zoom function. However, since the focal length of a single focus or focus switching type camera is determined, the present invention is applied to a single focus or focus switching type camera. In this case, the focal length detecting means 20 in FIG. 1 can be simplified. In this case, if the focal length information is stored in the memory of the CPU 1, it is possible to determine whether or not the photographing magnification is the magnification used for photographing a person only by obtaining the subject distance.

According to the above-described embodiment, even a beginner can relieve unsightly shadows on the face when shooting under direct light, especially when shooting with top light.

When the brightness of the subject is higher than the predetermined value and strobe light is not required, or when the strobe does not work because the subject is out of the reach of the strobe light, the strobe is not fired. Can be prevented.

[Effects of the Invention] As described above, according to the first aspect of the present invention, when the subject brightness by the photometric unit is higher than the predetermined value and the shooting magnification by the shooting magnification calculation unit is within the predetermined range, Since the strobe light value is lower than the strobe light value when the subject luminance is lower than a predetermined value by the photometric means, for example, when the subject is a person, it is prevented from rising white and becoming unnatural. Then, the strobe light emission can be controlled so that the person is properly exposed.

According to the second aspect of the present invention, in addition to the above effects, it is possible to prevent the battery from being consumed when the strobe light emission has no effect.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an electric circuit of a light emission control device showing one embodiment of the present invention, and FIG. 2 is a flowchart of a strobe light emission operation in FIG. 1 CPU (photographing magnification calculating means, light emission prohibition canceling means) 10 distance measuring means 20 focal length detecting means

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Suzuki 2-43-2 Hatagaya, Shibuya-ku, Tokyo Within Olympus Optical Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) G03B 15 / 05 G03B 7/00-7/28

Claims (3)

(57) [Claims] 1. A photometric unit for measuring the luminance of a subject, a distance detecting unit for detecting a distance of the subject, a focal length detecting unit for detecting a focal length of a photographing lens, and outputs of the distance detecting unit and the focal length detecting unit. A photographing magnification calculating means for obtaining a photographing magnification of the object using the control means, and a control means for controlling strobe light emission, wherein the control means is configured such that the object luminance by the light metering means is higher than a predetermined value and the photographing magnification calculation is performed. The light emission control device is characterized in that when the photographing magnification by the means is within a predetermined range, the strobe light amount value is lower than the strobe light amount value when the subject brightness is lower than a predetermined value by the photometric means. 2. The control means inhibits strobe light emission if the subject distance detected by the distance detecting means is longer than a predetermined value, and sets the subject brightness by the photometric means to a predetermined value if the subject distance is shorter than the predetermined value. 2. The light emission control device according to claim 1, wherein the strobe light emission is prohibited only when the shooting speed is higher than a predetermined value and the shooting magnification by the shooting magnification calculation means is not within a predetermined range. 3. The light emission control device according to claim 1, wherein the predetermined range is a photographing magnification of 1/20 to 1/80.